from __future__ import annotations
import numpy as np
import gdsfactory as gf
from gdsfactory.component import Component
from gdsfactory.components.rectangle import rectangle
from gdsfactory.components.taper import taper as taper_function
from gdsfactory.typings import (
ComponentSpec,
CrossSectionSpec,
LayerSpec,
)
[docs]
@gf.cell
def grating_coupler_rectangular(
n_periods: int = 20,
period: float = 0.75,
fill_factor: float = 0.5,
width_grating: float = 11.0,
length_taper: float = 150.0,
polarization: str = "te",
wavelength: float = 1.55,
taper: ComponentSpec = taper_function,
layer_slab: LayerSpec | None = None,
layer_grating: LayerSpec | None = None,
fiber_angle: float | None = None,
slab_xmin: float = -1.0,
slab_offset: float = 1.0,
cross_section: CrossSectionSpec = "xs_sc",
**kwargs,
) -> Component:
r"""Grating coupler with rectangular shapes (not elliptical).
Needs longer taper than elliptical.
Grating teeth are straight.
For a focusing grating take a look at grating_coupler_elliptical.
Args:
n_periods: number of grating teeth.
period: grating pitch.
fill_factor: ratio of grating width vs gap.
width_grating: 11.
length_taper: 150.
polarization: 'te' or 'tm'.
wavelength: in um.
taper: function.
layer_slab: layer that protects the slab under the grating.
layer_grating: optional layer for the grating. Defaults to the cross_section main layer.
fiber_angle: in degrees.
slab_xmin: where 0 is at the start of the taper.
slab_offset: from edge of grating to edge of the slab.
cross_section: for input waveguide port.
kwargs: cross_section settings.
.. code::
side view
fiber
/ / / /
/ / / /
_|-|_|-|_|-|___ layer
layer_slab |
o1 ______________|
top view _________
/| | | | |
/ | | | | |
/taper_angle
/_ _| | | | |
wg_width | | | | | |
\ | | | | |
\ | | | | |
\ | | | | |
\|_|_|_|_|
<-->
taper_length
"""
xs = gf.get_cross_section(cross_section, **kwargs)
wg_width = xs.width
layer = layer_grating or xs.layer
c = Component()
taper_ref = c << gf.get_component(
taper,
length=length_taper,
width2=width_grating,
width1=wg_width,
cross_section=cross_section,
)
c.add_port(port=taper_ref.ports["o1"], name="o1")
x0 = taper_ref.xmax
for i in range(n_periods):
xsize = gf.snap.snap_to_grid(period * fill_factor)
cgrating = c.add_ref(
rectangle(size=(xsize, width_grating), layer=layer, port_type=None)
)
cgrating.xmin = gf.snap.snap_to_grid(x0 + i * period)
cgrating.y = 0
if fiber_angle is not None:
c.info["fiber_angle"] = fiber_angle
c.info["polarization"] = polarization
c.info["wavelength"] = wavelength
slab_xmin = length_taper
for section in xs.sections[1:]:
slab_xsize = cgrating.xmax + section.width / 2
slab_ysize = width_grating + section.width
yslab = slab_ysize / 2
c.add_polygon(
[
(slab_xmin, yslab),
(slab_xsize, yslab),
(slab_xsize, -yslab),
(slab_xmin, -yslab),
],
layer=section.layer,
)
if layer_slab:
slab_xsize = cgrating.xmax + slab_offset
slab_ysize = width_grating + 2 * slab_offset
yslab = slab_ysize / 2
c.add_polygon(
[
(slab_xmin, yslab),
(slab_xsize, yslab),
(slab_xsize, -yslab),
(slab_xmin, -yslab),
],
layer_slab,
)
xport = np.round((x0 + cgrating.x) / 2, 3)
c.add_port(
name="o2",
port_type=f"vertical_{polarization}",
center=(xport, 0),
orientation=0,
width=width_grating,
layer=layer,
)
return c
if __name__ == "__main__":
# c = grating_coupler_rectangular(name='gcu', partial_etch=True)
gc = grating_coupler_rectangular(cross_section="xs_rc")
c = gf.routing.add_fiber_array(grating_coupler=gc)
print(c.ports)
c.show(show_ports=False)
